Photographic emulsion



Oct. 11, 1938. a H, CAR'ROLL l v2,132,866

PH'OTOGRAPHIC EMULSION 'Filed Maron 29, 1937 Emmen-mu;

INVENFOR:

OMJ

ATT RNEY ncred o-.11 o 1 Y 2,132,866A

UNITED STATES AP ATE1S1T` oi-Ficlaz PHOTOGRAPHE) EMULSION Burt H. Carroll, Rochester, N. Y., assigner to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey y y Application March 29, 1931,' serial No. 133,583 12 Claims. (Cl.` 95-7) This invention relates to .sensitizedfphotofor which the other dye does not sensitize; vfor graphic emulsions and more particularly to example, when the red sensitization produced by photographic emulsions, such as4 those of the dye A increases in the presence of dye B which gelatino-silver-halide type, containing a mixture sensitizes only for the green. When two or more 5 or combination of two ormore sensitizmgmadyes sensitize for approximately Athe same or 5 terials, at, least one of whichcooperates with'at kWidely overlapping spectral regions (as in anum- A least one other to alter the sensitivity of the ber of the eases to be described in the instant Aemulsion to a greater degreethan is possible application), supersensitizotion oon Still bode- With any one of the sensitizing materials alone. tested, because if supersensitization obtains in The sensitization produced by my combination is Such cases the total optical sensitization pro- 10 always greater, in some spectral region, than the duced by a Combination of two' or more dyes Will sum total of the sensitizations produced by the always'fbe greater, under favorable Conditions. separate sensitizing materials. The sensitizng than that which can be produced 'by any dye of materialsv of my combinations are substances the combination alone at any Conoentrationgenerally referred to as dyes and more partic-k The magnitude of the supersensitization depends 15 .ularly as dyes of the cyanine class. A upon the relative and absolute concentrations of It is known in the art of making photograhic 'the dyes in the emulsion and 0n the type of emulsionsvthat certain dyes of the cyanine class y Y emulsion. By suitable choice of conditions sualter the sensitivity of photographic emulsions of `persensitization can always be made Ato assume the gelatino-silver-halide type, when incorpo- Values Which are readily observable- 20 rated therein. The sensitizing effect produced M y application deals with emulsions containbythe dye does not increase vproportionally to ing supersensitizingmixtures or Combinations of Ithe amount of dye, but passes through a, maxonevor more sensitlzing dyes of the 8-alkyloxa- Iimum as the concentration is increased. Within callooyalliue salts# wherein, the 8-a1kyl group the range of concentrations most usefulr in praccOntains at least tWo Carbon atoms With one or 25 tice, the sensitivity increases vmuch lmore slowly more sensitizing dyes of the pseudoeyanine than the concentration of the dye. Likewise, the group. Just v110W the dyes of my mixtures oocombined eiect'of'two or more dyes on an emuloperate to give a supersensitizing eiect is not sionv is rarely equivalent to'the sum of'their known- I shall'refer to the mixtures as oom- 30' separate emects; in general' it is much 1ess. binations, although I do not intend to `imply ao Mostcommonly, the combined eect vis no greater that the dyes are Chemically Combinedthan 'the eiTect of a single one of the dyes em- An object of my invention, therefore. is to ployed in aV concentration equal to the `sum of. provide photographie' 1 emulsi0ns-fContainin8 a` the concentrations or al1 the dyes in the comsupersensitizins combination of cyanine dyes.

- bination. -Very frequently, the combined effect A further object is to provide a process for Seus- 35 50 point of which is supersensitized.

of two dyes is less than that of one of them itiZinE photographie emulsions With supersensalone. y ,Y itizing combinationsof cyanine dyes and to pro- I have' found with certain combinations of two Vide a method of increasing the sensitivity of K or more cyanine dyes, that thecombined sensiphotographie emulsions sensitized With cyanine 40 tization-is substantiallygreater, in some spectral dyes. A stili further object is to provide a photo- 40 region, than .that of anyone of the dyes in the vgraphic element comprising a Support coated' absence of the A other or others. I will call this with such, Super-sensitized emulsions. Other phenomenon supersensitiz'ation. In general, at more speoioobleotswilkbeeome apparent hereleast'l one dye of my combination may be said to inafterbe supersensitiged -by the' other or others. The The dyes which I employ in my supersensitiz- 45 dye which is supersensitized mayv be called the ing-'combinations are lsensitizers of photographic basic sensitizer and the other dye the superemulsions when used alone. While there is more sensitizer. However, the eiect may be mutualV than one manner of formulating and naming andthe dyes indistinguishable from the standthe dyes which I employ in practicing my inven- Supersensitization is a highly specic phe-v numbering and names used herein are in accordnomenon and is found only in mixtures or comance with those used during the development of binations of dyes from certain speciiic groups. the cyanine dye art to its present stage. I'he Supersensitization can be most readily observed, most probable formulas 'of representative dye- 55 when adye is supersensitized in aspectr'al region types are given below in order to clearly set 55 tion, it is believed that the formulas, systems of the natureof the materials employed in my supersensitiziig mixtures. These formulas should not be construed as limiting my invention except as indicatedin the appended claims. Among the' B-alkyloxac'arbocyanines, useful in practicing my inention are the following:V

Y, The S-alkyloxacarbocyanines rwhich can be represented bythe following general formula:

l. x. 'Y

In the above. formular, A represents an'alkyl" group of at least two carbon atoms, R and R represent alkyl groups and X represents an acid radical.; I have found it convenientto employ Y.the carbocyanine dye-,iodides r(where X .repre- 2o ever, other dye=salts, such as the chlorides, brosents iodine) inpracticing Amy invention.; VHowmides, perchlorates, alkylsulfates or alkyl-p-toluenesulfonates canbe employed,V for example. I haveA also found it advantageous to employ dyes wherein A represents an alkyl groupv of from two Yto four carbon atoms, such 4as ethyl,vr isobutyl,

l--hydroxyethyi or allyl groups,'for example, in practicing myf invention. More specically, I havefound dyes wherein Arrepresents ethyl ari-d n R and R represent methyl to be especially useful.A The nuclei of the dyes can carry sii-nple substituents which do not interfere with sensitizing properties, suchyas, for example, alkyl, chloro,v

alkoxy or amino groups. symmetrical and vunsymmetrical oxacarbocyanine dyes can be em-` ployed in practicing my invention.

The -alkyl'oxacarbcyanines can be'prepared' by reacting 1-methy1benzoxazole quaternary salts with trialkylortho esters of monobasic carboxylic y acids ofv three'or. more carbon atoms, in the presence of an organic base, e. g. dry pyridine, as described in US. Patent No. 1,962,12lf.4 By employingy mixtures ofsubstituted benzoxazole and unsubstituted benzoxa-zole quaternary salts, mixtures of symmetricaland unsymmetrical 8-a1kyloxacarbocyanine dyes can be obtained.

Among thepseudocyanine dyes which can'be empigoyed in practicing my invention are the following: Y L

'The 22'cya'm1neV dyes, which can be: represented by the following general formula RV R' \x The thia-2-'cyanine dyes, which can be represented by'the following general formula:

aisasee l The benzothia-2cyanine dyesfwhich can beA represented by the follewing general formula:

' The oxazolo2'cyanine dyes,v which can be represented by the following general formula:

i In all of the above formulas of pseudocyaniie dyes, R and R' represent alkyl groups and X represents an acid radical. 'I'he oxazolo-2cyanines can be substituted in the -position with substituents, such as alkyl or aryl groups ofthe benzene series, for example, phenyl. In practicing myn- Vention, I have found it convenient tc employ the pseudocyanine dye-iodides (wherein X represents iodine). However, other pseudocyanine salts can be` employed, suchf-for example as the chlorides, bromides, perchlorates, alkylsulfates or alkyl-p-toluenesulfonates. Ijhave further found it advantageous :.toeniployfy pseudocyanine dyes wherein R and R represent an alkyl group of from one toour carbon atoms. The dyes wherein R and R' represent ethyl are particularly usefuln practicing myinvention. The pseudocyanine dyes can be substituted in their nuclei 'with simple substituents which do not interfere with sensitizing properties, suchfor example as alkyl, chloro,falkoxy, or amino groups.

Brooker and Keyes, in the Journal of the American Society, vol. 5T, pages 2488-2491 (1935) have reviewed 4the literature pertaining to pseudocyaninej dyes and describe methods for'the preparation thereof. Oxazolopseudocyanine dyes are deu scribed in U. S. Patent No.;1,969,4fi6. 1 f

The objects 'of my invention can be accomplished by merely incorporating one-or more sensitizingI 8-alkyloxacarbocyanine dyes together with one or more sensitizing pseudocyanine dyes capable of supersensitizing the B-alkyloxfcarbocyanine in a photographic emulsion. My invention is particularly directed to the ordinarily empioyed gelatina-silver-halide emulsions. However, my supersensitizing combinations can Vbe ern-` `ployed in emulsions in which the carrier is other than gelatin, for example, a resinous substance or cellulosic derivative which has substantially no l deleterious eiect on the light-sensitivematerials. As silver halide emulsions, I include such emulsions as are commonlyV employed inthe art, for

example, ysilver chloride or silver bromide emulsions which can contain other salts which may be light-sensitive. By way of illustration,'theherein described.v supersensitized emulsions were pre-- pared employing an ordinary gelatina-silver-bro- Y sitization of the desired magnitude must be devin the 'arti- In practicing my invention, the dyes i may be varied widely from 5:1 to 1:5, for example. The most favorable. conditions for supersentermined by-experiment, the mannerof which will *be apparent to A'those skilled in the art upona complete perusal of these specifications.`

The methods of incorporating dyes inemulsions are simple'an'dwell known to those skilled of 'my combinations can be added separately-or together. It is convenient to add the` dyes sepaaisaseo Y carbocyanines with pseudocyanines likewise show supers'ensitizing effects; Thei 2,2dimethyl8 ethyloxacarbocyanines 'are' of particular utility in practicing my invention. Pseudocyanine dyes containing the 5,6-benzothianucleus are usually of lesser utility inpracticing'my invention.' 'I'he oxazolopseudocyanine dyes substituted in the 4- position of the oxazole nucleus by analkyl group, such as methyl, "or by an aryl group, such as phenyl, for example,vare especially useful in prac- -`ticing my invention.

Among others, the following combinations have been found'fto be `imrticularly useful: I Pteudocyaninu za'aimeoiyieethyiomearbcyaine iodide with l indiaan-affini idiae.

compatible with the emulsion,.substantially free from any deleteriouseffect onthe lightesensitive materials and capable of dissolving theA dyes. Methanol has proven satisfactory asa solvent for .the dyes in practicing my invention. The dyes -are advantageously incorporated in the nished,

washed emulsion and should be uniformly distributed throughout the emulsion. The emulsion can .then4 be converted into a photographic ele ment by coatingupon a support, such as glass, cellulose acetate, cellulose nitrate or other cellulose derivative or resin in a-manner well known in the art. f i

The accompanying drawing is by Way of illustration and'. depicts the supersensitizing effect of my new combinations. The figure of the drawing is a diagrammatic reproduction of three spectrograms showing, first, the sensitivity of 'a silver bromide emulsion containing an 8-alky1oxacarbo- Cyanine dye (represented by'thedot-and-dash line), second, the sensitivity'of the same silver bromide emulsion containing a pseudocyanine dye (represented by the dotted line) and third, the sensitivity of the same emulsion containing a mixture or combination of the said 8-alkyloxacarbocyanine dye r`with the said pseudocyanine dye centration of 10 mg. per liter of emulsion; curve vni B represents the sensitivity of the same emulsion containing 3,1'- diethyl-i-phenyloxazolo-2- cyanine iodide in a concentration of 10 mg. per liter of emulsion, and curve C represents the same emulsion containing 2,2-dimethyl-B-ethyloxacar-` bocyanine iodide and 3,1diethyl-4`phenyloxa zolo-2'cyanine iodide in concentrations of 10 mg. and 15 mg. per liter, respectively. The sensitivity of the emulsion represented by curve C, as

measured through a Minus Blue Wratten No. 12

Filter, is about 40% greater than that of the emulsion represented by curve A.

The spectrograms corresponding to the figures of the accompanying drawing were made in a wedge spectrograph. The intensity of each horizontal line was approximately one-tenth that `at the next lower line. Where the spectrograms were compared as in the drawing, the exposures were for the same time and the test plates of each dye were developed together.

The other of my combinations of 8-alkyloxa- In general, it can be said ofemy combinations thatthe oxacarbocyanine is ythe d yesupersensitired (basic supersensitizer) and that the pseudocyanine is the supersensitizer.. However, the

f nature of this relationship between the dyes of my the manner in which my invention is carried out and the principles of sensitizing photographic emulsions .with supersensitizing combinations, such as described herein. While I have illustrated only combinations containingtwo dyes, my combinations can as well contain one oxacarbocyanine cooperating' with two or more pseudocyanine dyes. Likewise my combinations can contain one pseudocyanine dye cooperating withvtwo or more oxacarbocyanine dyes.

Cyanine dyes containing hydroxyalkyl groups can be -prepared from cyclammonium quaternary salts prepared by reacting heterocyclic nitrogen bases with halohydrins, e. g. ethylene halohydrins and propylene halohydri'ns. It is advantageous to employ the bromohydrins. The heterocyclic nitrogen base and the bromohydrin are merely heated together for several hours, e. g. 25 to 30 hours or longer, at about 100 C., though 150 C.

can be employed. 'An excess of the bromohydrin is vadvantageously employed. Following the reaction, the solid reaction product is advantageously converted to the iodide by treatment with p'otassium iodide. This can be accomplished by dissolving the crude Quaternary bromide in hot water and treating the solution with a hot aqueous solution of potassium iodide (1 g. per cc. of l water). Cyanine dyes containing hydroxyalkyl groups are describedvin the application of Leslie .G. S. Brooker and Lloyd A. Smith, Serial No.

dye.

2. A photographic gelatina-silver-halide emulsion containing a supersensitizing combination of at least one sensitizing dye selected from the group consisting -of 8-alkyloxacarbocyanne dyes in which the 8-alkyl group contains at least two carbon atoms, with at least one sensitizi'ng pseudocyanine dye.

3.. A photographic gelatino-silver-halide emulsion containing a supersensitizing combination vof at least one sensitizing dye selected fromthe group consisting of 8-alkyloxacarbocyanine dyes in which the 8-alkyl group contains at least two carbon atoms, with at least one sensitizing thia- 2cyanine dye.

4. A photographic gelatina-silver-halide em sion containing a supersensitizing combination of at least one sensitizing dye selected from the group consisting lof 8alkyloxacarbocyanine dyes s in which the 8-alkyl group contains atleast two s carbon atoms, with at least one sensitizing 2,2-

cyanine dye. I

5. A photographic gelatino-silver-halide emulsion containing a supersensitizing combination of at least one sensitizing dye selected from the group consisting of 8-alkyloxacarbocyanine dyes in whichthe 8-alkyl group contains at least two `carbon atoms, with at least one sensitizing oxazolo-2cyanine dye.- l

6. A photographic gelatino-silver-halide emulsion containing a supersensitizing combination of at least one 2,2-dimethylf8ethyloxacarbo cyanine dye with at least one thial2-cyani.ne

dye. v 7. A photographic gelatine-silver-halide' emull vsion containing a supersensitizing combination of at least one 2,2-dimethyl-8-ethyloxacarbo- 2,2'cyanine halide.

1 aisance 8. A photographic gelatino-sllver-halide emulsion containing a supersensitizng combination of at least one 2,2dimethyl8ethyloxacarbo cyanine dye with at least one oxazolo2cyanine dye.

9. A photographic gelatina-silver-halide emulsion containing a supersensitizing combination of at least one 2,2'-dimethyl--ethyloxacarbophenyloxazolo-2'v-cyanine halide. 12o

, 12. A photographic gelatino-silver-halide emulsion containing a supersensitizing combination of at least one .sensitizing dye selected from "the .group consisting of 8-a1kyloxacarbocyanine dyes in which the 8-alkyl group containsy at least 25 two carbon atoms, with at least one sensitizing dye selected'from the group consisting of 2,2'- cyanine dyes, thia-2cya,nine dyes, Selena-2- cyanine dyes, 3,4-b'enzothia-2f-cyanine dyes and BURT H. CARROLL.

cyanine' dye with at least one 2,2cyanine -dye. 

